This invention relates to stents and methods of maintaining patency of a body lumen such as the ureter using stents.
A ureter is a tubular passageway in a body that conveys urine from a kidney to a bladder. Urine is transported through the ureter under the influence of hydrostatic pressure assisted by contractions of muscles located within the walls (lining) of the ureter. A urological condition that some patients experience is ureteral blockage or obstruction. Some common causes of ureter blockage are the formation of tumors or abnormalities within the ureteral lining or the formation and passage of kidney stones.
Ureteral stents are medical devices designed to extend through the ureter and are frequently used to bypass the ureter to facilitate drainage from a kidney to the bladder when a ureter becomes blocked or obstructed. Generally, these stents are made from small diameter tubing of a biocompatible plastic. Ureteral stents may have multiple side holes to enhance drainage and typically include retention hooks, pigtail curls, coils, or malecots extending from both the kidney (distal) and bladder (proximal) ends of the tubing to prevent the migration of the ureteral stent after placement within the ureter.
The present invention generally relates to draining fluids from the kidney to the bladder of a patient with a stent. Devices and methods according to the invention are typically used in the treatment of patients suffering from an obstructed ureter to address and relieve urinary retention while minimizing patient discomfort. It is an object of the invention to maintain the ureter open and able to pass fluids from the kidney to the bladder. It is another object of the invention to minimize patient discomfort.
In one aspect, the invention relates to a ureteral stent. The ureteral stent includes an elongated portion, a retention portion extending from one end of the elongated portion, and a flared portion extending from the other end of the elongated portion. The elongated portion has a length sufficient to extend substantially within the ureter from the kidney to the bladder and defines a lumen extending within. The retention portion extends from a distal end of the elongated portion and is configured for placement and retention within the kidney. The retention portion includes an interior space in communication with the lumen of the elongated portion and at least one opening in communication with the interior space for urine drainage from the kidney to the ureteral stent. The flared portion extends from a proximal end of the elongated portion and is configured for placement substantially within the bladder. The flared portion curves outward while extending from the elongated portion and includes an elastic member for maintaining the shape of the flared portion in an expanded shape when located within the bladder. The flared portion is collapsible to allow entry of the flared portion into the bladder through the urethra.
Embodiments of this aspect of the invention can include the following features. For example, the elastic member of the flared portion may be made from a shape-memory material or a superelastic material, such as for example, a nickel-titanium alloy, or an elastomeric material. In some embodiments, the elastic member is a ring or loop of material that is embedded within or attached to the flared portion. The shape of the ring or loop may be round, oval, or even elliptical, or it may even be patterned to have a sinusoidal or saw-tooth shape. In other embodiments, the elastic member may include a plurality of collapsible spokes. These collapsible spokes have a first and a second end. The first end of the spokes is attached to a wall of the flared portion and the second end is attached to a hub. In an expanded state, the spokes extend radially from the hub. In a collapsed state, the spokes extend longitudinally from the hub.
In some embodiments, the flared portion may further include a valve that allows fluid to pass from the elongated portion through the valve, out of the flared portion, and into the bladder, but not from the bladder back into the elongated portion. The flared portion itself is made from a thin flexible material and may be corrugated. The retention portion, which is located within the kidney when the ureteral stent is placed within the patient, may be made from a shape-memory or a superelastic material and may have a coil or other retention structure shape. In other embodiments, the entire ureteral stent including the elongated portion, the retention portion, and the flared portion is sized to fit within a cystoscope.
In general, in another aspect, the invention features a method of inserting within a urinary tract a ureteral stent such as the stent described above. The method includes inserting the stent into the urinary tract of a patient and positioning the ureteral stent within the ureter of the patient such that the retention portion is within the kidney and the flared portion is within the bladder. The method may also include collapsing the flared portion of the ureteral stent prior to insertion and allowing the flared portion to expand within the bladder. The method may further include providing a cystoscope sized to receive the ureteral stent and using the cystoscope to insert and position the ureteral stent within the urinary tract of the patient.
The foregoing and other objects, aspects, features, and advantages of the invention will become more apparent from the following description and from the claims.